import math
def main():
    x1, y1, x2, y2 = map(float, input().split())
    b = abs(x2 - x1)
    h = abs(y2 - y1)
    d = math.sqrt(b ** 2 + h ** 2)
    print("{0:.8f}".format(d))


if __name__ == "__main__":
    main() import math math def main():
    x1, y1, x2, y2 = map(float, input().split())
    b = abs(x2 - x1)
    h = abs(y2 - y1)
    d = math.sqrt(b ** 2 + h ** 2)
    print("{0:.8f}".format(d)) main x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 b = abs(x2 - x1) b abs(x2 - x1) abs x2 - x1 x2 x1 h = abs(y2 - y1) h abs(y2 - y1) abs y2 - y1 y2 y1 d = math.sqrt(b ** 2 + h ** 2) d math.sqrt(b ** 2 + h ** 2) math.sqrt math sqrt b ** 2 + h ** 2 b ** 2 b 2 h ** 2 h 2 print("{0:.8f}".format(d)) print "{0:.8f}".format(d) "{0:.8f}".format "{0:.8f}" format d if __name__ == "__main__":
    main() __name__ == "__main__" __name__ "__main__" main() main def main():
    x1, y1, x2, y2 = map(float, input().split())
    b = abs(x2 - x1)
    h = abs(y2 - y1)
    d = math.sqrt(b ** 2 + h ** 2)
    print("{0:.8f}".format(d)) def main():
    x1, y1, x2, y2 = map(float, input().split())
    b = abs(x2 - x1)
    h = abs(y2 - y1)
    d = math.sqrt(b ** 2 + h ** 2)
    print("{0:.8f}".format(d)) main
import math
def main():
    x1, y1, x2, y2 = map(float, input().split())
    b = abs(x2 - x1)
    h = abs(y2 - y1)
    d = math.sqrt(b ** 2 + h ** 2)
    print("{0:.8f}".format(d))


if __name__ == "__main__":
    main()